This invention relates to an apparatus for aligning a rotating part such as a spindle of a milling machine to a predetermined reference position.
Apparatus for orientating rotating machinery have found acceptance in the machine tool industries especially for providing a means for accurately and automatically repositioning spindles of milling machines and tool holders for such machines. Traditional spindle systems are expensive and complicated. One such system utilizes a solenoid operated mechanical shotpin to engage an alignment holes on the spindle. Mechanical systems such as these often acquire complicated sequencing logic to properly control the spindle during the alignment or orientation procedure. Alignment or orientation is typically accomplished by stopping the spindle, switching to a low speed gear and then introducing a creep voltage which slowly moves the spindle until the mechanical shotpin engages the alignment hole. Alternatively, alignment or orient can be achieved by using a proximity switches which are activated by magnetic material or original generators. Such devices are illustrated by Cook in U.S. Pat. No. 3,487,283, Peters in U.S. Pat. No. 3,395,323 or by Dickinson et al in U.S. Pat. No. 3,636,425. A problem associated with these systems is that they do not acquire the reference position rapidly, e.g., the reference position is often overshot, therein requiring the spindle to rotate through an entire revolution to regain the reference position. Other orient systems replace the mechanical shotpin and solenoid by utilizing transducers in a feedback position loop as illustrated by Whetham in U.S. Pat. No. 3,777,125. These resolver systems generate feedback pulses and require complicated and extensive signal conditioning electronics.
The present invention relates to a reorientation system for a machine tool having a normal and an orientation mode of operation, comprising: spindle means, including a spindle for rotating relative to a stationary portion of the machine tool in response to electrical signals input thereto, the spindle means includes a first reference indicator located on the spindle and situated perpendicular to the spindle's axis of rotation, and a stationary portion of the machine tool wherein when the first reference indicator is colinear with the second reference indicator, the spindle has achieved a reoriented or reference position.
The invention relates to a system having a signal generating means comprising: a half-round magnet attached to a spindle and mounted relative to a first reference indicator such that the ends of the half-round magnet are aligned to the first reference indicator and a pair of opposingly mounted magnetic switches magnetically coupled to the magnet and mounted to the stationary portion and aligned relative to a second reference indicator for generating a first signal when the first magnetic switch is activated by the magnet and a second signal when the second magnetic switch is activated by the magnet. The system further comprises gating means, responsive to the first and second signals for generating an orient signal wherein the orient signal has a first level during a first interval of time corresponding to the occurrence of the first signal, a second level during a second interval of time corresponding to the occurrence of the second signal and oscillates between the first and the second levels during a third interval of time corresponding to the simultaneous occurrence of the first and the second signals. In addition the system includes a controller means for supplying to the spindle means driving signals during the normal mode of operation to cause the spindle means to rotate at a predetermined speed in a predetermined direction and for supplying to the spindle means during the orientation mode the orient signals to cause the spindle means to be aligned to the reference orientation.
It is a broad object of the present invention to remedy the deficiencies in the prior art. More specifically, it is an object to orient a spinning member to its reference position independent of speed of rotation. It is further object of the present invention to provide a simple, low cost apparatus having few mechanical parts.